Help please!!

rlowery

Active Member
I bought an evenheat ko 18 several months ago and have been second guessing the low temps, so I fired up my homemade oven with an auberins pid and decided to check it with another pid and thermocouple.
I drilled a hole thru the door and inserted a k thermocouple and the readings between the 2 are 30 degrees. I hate to drill a hole in my knew oven to check the pid and thermocouple against the rampmaster control. I put several oven thermometers in the oven and nothing seems to line up with either pid. Any advice would be greatly appreciated. Ed Caffrey gave me the idea on the extra pid and thermocouple, I didn't buy the one that he recommended because I already had one and wanted to save a little money. Thanks in advance for your help.
Rickey
 
The Evenheat thermocouple is accurate where it is placed and your other is accurate where it is placed. A 30 degree difference between different places in the oven is not uncommon. Longer times will lead to closer temperatures, but don't over think it.
 
Seems I've been talking about this a lot lately. Heat treat ovens that are sold as "knifemaking" ovens carry different ratings of accuracy, expressed in percentages from the setpoint. The best ones generally carry a 2-3% variance, and it goes up from there. Generally the cost of the oven can be directly related to it's percentage of accuracy. Based on my experiences, Paragon ovens, while tending to be more expensive, also tend to have the tightest tolerances when it comes to temps.... other brands fall in line behind Paragon, with the lower prices indicating a wider variance of temp.
 
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i would get a Templistik or two. these are crayons that melt at precise temperatures. i took a piece of scrap steel, placed it in the furnace where blades would sit, and adjusted my thermocouples so they were with a inch or so of the test piece. one thermocouple was attached to a controller, the second to a display. when the crayon melted, the displays were with 10 degrees F of each other, so i know my temp display is accurate. try to adjust your thermocouples so they are near the center of your blade.
 
thanks for the replies I really appreciate yall sharing your knowledge and experience.
I am going to do a couple of blades at the temps I have been doing them and have them
rockwelled. I have tested blades I have done in both ovens and have been satisfied with them.
I just want to make sure I am getting the most out of the steel. I owe this to my customers.
 
thanks for the replies I really appreciate yall sharing your knowledge and experience.
I am going to do a couple of blades at the temps I have been doing them and have them
rockwelled. I have tested blades I have done in both ovens and have been satisfied with them.
I just want to make sure I am getting the most out of the steel. I owe this to my customers.

You might try adding a 1" slab of steel to the bottom of your oven (ideally covering the entire floor). The thermal mass will do wonders in terms of producing uniform temps inside. I'm not familiar with your particular oven so make sure nothing comes in contact with the coils - you might need to make spacers from soft firebrick.

If you want to take it "over the top" sandblast the steel plate and coat it with a ceramic wash designed to coat steel crucibles (Steve Chastain mentions the product in his aluminum foundry book). The performance improvement will be marginal, but the steel will stay nice.
 
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